Managed Extensions: Versioning Collection Classes

Maintaining a Boolean Member to Indicate a "Dirty" Collection

I used a numeric field to track the version number associated with a given enumerator object. I did this to handle scenarios in which the client might retrieve multiple enumerator objects from a single collection object. As a result, each time the data is changed the client code needs to reacquire each enumerator object that is made obsolete. Depending on the complexity of your needs, you could use a simple boolean member to indicate whether or not the collection is "dirty" or changed. The main difference being that if you use such a technique you would be marking the collection dirty for all clients of a particular instance of the collection. So it really comes down to the needs of your applications.

Looking Ahead

The past three (3) articles have illustrated the technique of creating two additional classes to the class that you're enumerating—a collection class (IEnumerable-derived) and an enumerator class (IEnumerable-derived). The next article will show how you can combine these two interfaces into a single class and explains when you would want to do that and when it would not be a good idea.

About the Author

The founder of the Archer Consulting Group (ACG), Tom Archer has been the project lead on three award-winning applications and is a best-selling author of 10 programming books as well as countless magazine and online articles.